#app3 {
    
}

#app3 > .square {
    border: 1px solid gray;
    width: 10vw;
    height: 10vw;
    margin: 10vw 0 0 10vw;
    transition: all 0.5s;
}
#app3 > .square.active {
    transform: translateX(100%);
}